Amateur-built HORNET N707BD accident near Camp Verde, Arizona

Probable cause

The in-flight separation of the exhaust clamps for an undetermined reason, which resulted in the exhaust system striking the wooden propeller.

NTSB analysis

The pilot reported that during cruise flight, the engine made a sound akin to a “buzz saw” that required him to initiate a forced landing to a nearby field. During the landing roll the nosewheel separated and the pusher-type engine separated from the mount assembly, impacting into the cockpit area. The pilot stated that a postaccident examination of the airplane revealed that the exhaust clamps had separated from the support structure while in-flight. A section of the exhaust system then struck the wooden propeller blades. Examination of the airplane by a Federal Aviation Administration inspector revealed the both wooden propeller blades had been sheared approximately six inches outboard of the blade root. Seven of the eight engine mount bolts were sheared at the adapter plate and the eighth bolt was missing. The separated exhaust clamps were not recovered for examination.

Text from the NTSB. Open the NTSB docket for WPR10LA317 for the full record.